The kinetics of an enzyme is measured as a function of substrate concentration in the presence and absence of 2 mM inhibitor. The data from the experiments are shown below: [S] (uM) Vo ( uM/min ) Vo ( uM/min ) with 2 mM inhibitor.
[S] (mM) Vo ( mM/min ) Vo ( mM/min ) with 2 mM inhibitor
3 10.4 4.1
5 14.5 6.4
10 22.5 11.3
30 33.8 22.6
90 40.5 33.8
a). Please draw a set of Vo versus [S] and corresponding double reciprocal plots to illustrate the effects of increasing concentrations of the inhibitor on the kinetics of the enzyme. b). What are the apparent Vmax and Km in the absence and in presence of the inhibitor? c). What kind of inhibition is it? d). What is the KI of the inhibitor?
The kinetics of an enzyme is measured as a function of substrate concentration in the presence and absence of 2 mM inhibitor. The data from the experiments are shown below: [S] (uM) Vo ( uM/min ) Vo ( uM/min ) with 2 mM inhibitor.
[S] (mM) Vo ( mM/min ) Vo ( mM/min ) with 2 mM inhibitor
3 10.4 4.1
5 14.5 6.4
10 22.5 11.3
30 33.8 22.6
90 40.5 33.8
a). Please draw a set of Vo versus [S] and corresponding double reciprocal plots to illustrate the effects of increasing concentrations of the inhibitor on the kinetics of the enzyme. b). What are the apparent Vmax and Km in the absence and in presence of the inhibitor? c). What kind of inhibition is it? d). What is the KI of the inhibitor?
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Enzyme Inhibition Kinetic
1. What is the advantage of using a substrate concentration near the Km in I50 determinations?
2. Estimate the I50 from the data below. How did you come to this conclusion?
[I] (mM) Activity (âA/minute)
0 0.53
3.75 0.38
7.5 0.29
15 0.19
30 0.11
60 0.05
120 0.02
3. The data in the table below were obtained by performing Km determination experiments in the absence of inhibitor and in the presence of two different inhibitors.
Velocity (µmol/min) | ||||
Substrate (mM) | No Inhibitor | Inhibitor 1 (1 mM) | Inhibitor 2 (1 mM) | |
0.25 | 0.06 | 0.02 | 0.02 | |
0.5 | 0.10 | 0.05 | 0.04 | |
1 | 0.17 | 0.08 | 0.07 | |
2 | 0.25 | 0.14 | 0.10 | |
4 | 0.33 | 0.22 | 0.13 | |
8 | 0.40 | 0.31 | 0.16 |
a. What type of inhibitor is Inhibitor 1? Why?
b. What type of inhibitor is Inhibitor 2? Why?
c. What are the Ki values for Inhibitor 1 and Inhibitor 2?